Battery management systems (BMS) usually take charge of calculating voltage levels of individual cells in a battery to protect the battery from being overcharged or over-discharged, and monitoring signal transmission inside/outside of the battery. In existing technologies, nearly all of battery-driving products need the battery management systems.
Since it is difficult to assure all the batteries to have absolute equalities during battery manufacturing, some problems may occur when such batteries are electrically connected in series to form a battery pack. For example, during charging of a battery module, even if some battery units in the battery module are still not saturated, some other battery units may have been overcharged. During discharging of the battery module, when some battery units still have power, some other battery units may have been over-discharged. In addition, if the battery units get overcharged or over-discharged for a long time, battery constructing materials may be degraded. As a result, the difference between characteristics of the battery units will be amplified by such degradation.
In order to solve the above problems, in existing technologies, battery management systems are used to balance power of the battery units. Conventionally, there are two types of power balancing methods: one is called passive power balance and the other is called active power balance. In the passive power balance method, redundant power of the battery units is transformed to heat by resistances and then dissipated. However, such passive power balance method can only be realized during charging. The active power balance method adopts a power transition manner, in which redundant power of the battery modules is transmitted to corresponding battery units with less power. Such active power balance method can be realized either in charging or discharging to meet broader needs.
However, the conventional battery management systems with the active power balance method employ DC/DC converters to convert the voltage of all the battery units of the battery pack so as to charge the given battery units needed to be charged. However, such process needs long balance time. In addition, the conventional active power balance method requires many judging and starting steps so that efficiency thereof is low as well.
Most battery management systems of general electric bicycles and general electric motorcycles adopt the passive power balance method to balance among the batteries or the battery modules due to cost consideration. Further, periodically collecting parameters of each battery, including voltage, current, and temperature, etc., is desired.
Generally, a charger can charge the battery under two charging modes, one is called normal charge mode and the other is called variable charge mode. In the normal charge mode, high charging current is adopted at the beginning stage so as to quickly charge the battery, and when the battery is charged near saturation, the charging current is reduced so as to slowly charge the battery. However, in the normal charge mode, two charging ports are usually needed for switching between the stages. In the variable charge mode, only one single charging port is needed for charging the battery with a variable current.
However, in the battery management systems with the passive power balance method, there is no communication between the battery management systems and the exterior chargers, so the battery management systems can only be set to one charging mode, which is not compatible to the chargers under the other charging mode.
In addition, with different technological focus of the chargers and the battery management systems, generic battery suppliers do not manufacture the chargers themselves. Thus, it is difficult for the charger suppliers to neatly meet different charging functions of the battery management systems.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.